The synthesis and utility of a wide range of block copolymers have advanced rapidly in the past few years. The type contemplated herein may be generally described as those copolymers having at least two polymer blocks of monoalkenyl arenes and at least one polymer block of a conjugated diene as well as hydrogenated counterparts of these products as more fully described hereinafter.
Due to the hydrocarbon structure of all parts of these block copolymers, their utility either alone or compounded has been limited in certain applications, primarily because of deficient adhesiveness toward other surfaces such as metals, wood, leather, polyvinylchloride and the like such as other polymers including polyurethanes, polychloroprene or adhesive compositions. These deficiencies become apparent for example in the construction of shoes and in the manufacture of multi-ply films. In shoe manufacture the soling material may be either molded, sewn or adhered to the upper, the upper being made of fabric, leather or polyvinylchloride, for example. One of the drawbacks of unmodified block polymer compositions in such constructions has been unsatisfactory adherence of soles made from the block polymer to these uppers especially under wet conditions when using normal commercial shoe assembly adhesives.
In the shoe industry, two generally accepted types of adhesives are employed, namely, neoprene and polyurethane types. By neoprene is meant the general class of polychloroprenes, while by polyurethanes is meant the condensation products of diisocyanates and polyesters or polyethers. In the past, it has been noted that even with the aid of these adhesives between the sole and the uppers, a lack of satisfactory adhesion may occur when one component of the assembly is an unmodified block copolymer composition.